It has long been known to provide a sabot, or sleeve, of plastic on a sub-caliber projectile to serve as a carrier for the projectile in the bore of the barrel of a full-caliber weapon. Such combinations of sub-caliber projectile and full-caliber sabot are commonly used in naval or field artillery and tank weapon rounds, similar devices have also been scaled down for use in rifles.
Usually such combinations of projectile and plastic sabot have been fitted into the mouth of a metallic shell, which contains the propellant charge and a means of detonating that propellant.
Exemplary of such plastic sabots are those disclosed in U.S. Pat. No. 3,005,408 to Prossen, et al of Oct. 24, 1961 and U.S. Pat. No. 3,551,972 to Engel of Jan. 5, 1971.
Such combinations may also be inserted into the breech of a weapon ahead of a separate propellant charge as disclosed in U.S. Pat. No. 3,148,472 to Hegge, et al of Sept. 15, 1964.
In U.S. Pat. No. 384,574 to Hawley of June 12, 1888, it was proposed to interpose a spring between the base of a projectile and a series of leather washers, mounted on a rear projection of the projectile, so that the spring would throw off the washers after the projectile was fired.
None of the above patents however, teach a one-piece cartridge which combines the sabot/projectile and the propellant compartment into a single body which is inseparable until detonation of the propellant.
The prior art has also taught the use of lateral and longitudinal grooves on the interior, or exterior surfaces of the sabot to aid in the controlled disintegration of the sabot during, or subsequent to, discharge of the projectile as shown in the above mentioned Prossen U.S. Pat. No. 3,005,408 and Engel U.S. Pat. No. 3,551,972.
Such disintegration of the sabot can lead to serious accuracy problems if a part of the disintegrating sabot should strike the projectile.
Other patents of interest in the sabot field are U.S. Pat. No. 2,669,930 to Darby of Feb. 23, 1954 and U.S. Pat. No. 2,992,612 to Critchfield of July 18, 1961.